1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Test cases for compiler-based stack variable zeroing via
4 * -ftrivial-auto-var-init={zero,pattern} or CONFIG_GCC_PLUGIN_STRUCTLEAK*.
5 * For example, see:
6 * "Running tests with kunit_tool" at Documentation/dev-tools/kunit/start.rst
7 * ./tools/testing/kunit/kunit.py run stackinit [--raw_output] \
8 * --make_option LLVM=1 \
9 * --kconfig_add CONFIG_INIT_STACK_ALL_ZERO=y
10 *
11 */
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13
14 #include <kunit/test.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/string.h>
19
20 /* Exfiltration buffer. */
21 #define MAX_VAR_SIZE 128
22 static u8 check_buf[MAX_VAR_SIZE];
23
24 /* Character array to trigger stack protector in all functions. */
25 #define VAR_BUFFER 32
26
27 /* Volatile mask to convince compiler to copy memory with 0xff. */
28 static volatile u8 forced_mask = 0xff;
29
30 /* Location and size tracking to validate fill and test are colocated. */
31 static void *fill_start, *target_start;
32 static size_t fill_size, target_size;
33
34 static bool stackinit_range_contains(char *haystack_start, size_t haystack_size,
35 char *needle_start, size_t needle_size)
36 {
37 if (needle_start >= haystack_start &&
38 needle_start + needle_size <= haystack_start + haystack_size)
39 return true;
40 return false;
41 }
42
43 /* Whether the test is expected to fail. */
44 #define WANT_SUCCESS 0
45 #define XFAIL 1
46
47 #define DO_NOTHING_TYPE_SCALAR(var_type) var_type
48 #define DO_NOTHING_TYPE_STRING(var_type) void
49 #define DO_NOTHING_TYPE_STRUCT(var_type) void
50
51 #define DO_NOTHING_RETURN_SCALAR(ptr) *(ptr)
52 #define DO_NOTHING_RETURN_STRING(ptr) /**/
53 #define DO_NOTHING_RETURN_STRUCT(ptr) /**/
54
55 #define DO_NOTHING_CALL_SCALAR(var, name) \
56 (var) = do_nothing_ ## name(&(var))
57 #define DO_NOTHING_CALL_STRING(var, name) \
58 do_nothing_ ## name(var)
59 #define DO_NOTHING_CALL_STRUCT(var, name) \
60 do_nothing_ ## name(&(var))
61
62 #define FETCH_ARG_SCALAR(var) &var
63 #define FETCH_ARG_STRING(var) var
64 #define FETCH_ARG_STRUCT(var) &var
65
66 /*
67 * On m68k, if the leaf function test variable is longer than 8 bytes,
68 * the start of the stack frame moves. 8 is sufficiently large to
69 * test m68k char arrays, but leave it at 16 for other architectures.
70 */
71 #ifdef CONFIG_M68K
72 #define FILL_SIZE_STRING 8
73 #else
74 #define FILL_SIZE_STRING 16
75 #endif
76
77 #define INIT_CLONE_SCALAR /**/
78 #define INIT_CLONE_STRING [FILL_SIZE_STRING]
79 #define INIT_CLONE_STRUCT /**/
80
81 #define ZERO_CLONE_SCALAR(zero) memset(&(zero), 0x00, sizeof(zero))
82 #define ZERO_CLONE_STRING(zero) memset(&(zero), 0x00, sizeof(zero))
83 /*
84 * For the struct, intentionally poison padding to see if it gets
85 * copied out in direct assignments.
86 * */
87 #define ZERO_CLONE_STRUCT(zero) \
88 do { \
89 memset(&(zero), 0xFF, sizeof(zero)); \
90 zero.one = 0; \
91 zero.two = 0; \
92 zero.three = 0; \
93 zero.four = 0; \
94 } while (0)
95
96 #define INIT_SCALAR_none(var_type) /**/
97 #define INIT_SCALAR_zero(var_type) = 0
98
99 #define INIT_STRING_none(var_type) [FILL_SIZE_STRING] /**/
100 #define INIT_STRING_zero(var_type) [FILL_SIZE_STRING] = { }
101
102 #define INIT_STRUCT_none(var_type) /**/
103 #define INIT_STRUCT_zero(var_type) = { }
104
105
106 #define __static_partial { .two = 0, }
107 #define __static_all { .one = 0, \
108 .two = 0, \
109 .three = 0, \
110 .four = 0, \
111 }
112 #define __dynamic_partial { .two = arg->two, }
113 #define __dynamic_all { .one = arg->one, \
114 .two = arg->two, \
115 .three = arg->three, \
116 .four = arg->four, \
117 }
118 #define __runtime_partial var.two = 0
119 #define __runtime_all var.one = 0; \
120 var.two = 0; \
121 var.three = 0; \
122 var.four = 0
123
124 #define INIT_STRUCT_static_partial(var_type) \
125 = __static_partial
126 #define INIT_STRUCT_static_all(var_type) \
127 = __static_all
128 #define INIT_STRUCT_dynamic_partial(var_type) \
129 = __dynamic_partial
130 #define INIT_STRUCT_dynamic_all(var_type) \
131 = __dynamic_all
132 #define INIT_STRUCT_runtime_partial(var_type) \
133 ; __runtime_partial
134 #define INIT_STRUCT_runtime_all(var_type) \
135 ; __runtime_all
136
137 #define INIT_STRUCT_assigned_static_partial(var_type) \
138 ; var = (var_type)__static_partial
139 #define INIT_STRUCT_assigned_static_all(var_type) \
140 ; var = (var_type)__static_all
141 #define INIT_STRUCT_assigned_dynamic_partial(var_type) \
142 ; var = (var_type)__dynamic_partial
143 #define INIT_STRUCT_assigned_dynamic_all(var_type) \
144 ; var = (var_type)__dynamic_all
145
146 #define INIT_STRUCT_assigned_copy(var_type) \
147 ; var = *(arg)
148
149 /*
150 * @name: unique string name for the test
151 * @var_type: type to be tested for zeroing initialization
152 * @which: is this a SCALAR, STRING, or STRUCT type?
153 * @init_level: what kind of initialization is performed
154 * @xfail: is this test expected to fail?
155 */
156 #define DEFINE_TEST_DRIVER(name, var_type, which, xfail) \
157 /* Returns 0 on success, 1 on failure. */ \
158 static noinline void test_ ## name (struct kunit *test) \
159 { \
160 var_type zero INIT_CLONE_ ## which; \
161 int ignored; \
162 u8 sum = 0, i; \
163 \
164 /* Notice when a new test is larger than expected. */ \
165 BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE); \
166 \
167 /* Fill clone type with zero for per-field init. */ \
168 ZERO_CLONE_ ## which(zero); \
169 /* Clear entire check buffer for 0xFF overlap test. */ \
170 memset(check_buf, 0x00, sizeof(check_buf)); \
171 /* Fill stack with 0xFF. */ \
172 ignored = leaf_ ##name((unsigned long)&ignored, 1, \
173 FETCH_ARG_ ## which(zero)); \
174 /* Verify all bytes overwritten with 0xFF. */ \
175 for (sum = 0, i = 0; i < target_size; i++) \
176 sum += (check_buf[i] != 0xFF); \
177 /* Clear entire check buffer for later bit tests. */ \
178 memset(check_buf, 0x00, sizeof(check_buf)); \
179 /* Extract stack-defined variable contents. */ \
180 ignored = leaf_ ##name((unsigned long)&ignored, 0, \
181 FETCH_ARG_ ## which(zero)); \
182 /* \
183 * Delay the sum test to here to do as little as \
184 * possible between the two leaf function calls. \
185 */ \
186 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
187 "leaf fill was not 0xFF!?\n"); \
188 \
189 /* Validate that compiler lined up fill and target. */ \
190 KUNIT_ASSERT_TRUE_MSG(test, \
191 stackinit_range_contains(fill_start, fill_size, \
192 target_start, target_size), \
193 "stackframe was not the same between calls!? " \
194 "(fill %zu wide, target offset by %d)\n", \
195 fill_size, \
196 (int)((ssize_t)(uintptr_t)fill_start - \
197 (ssize_t)(uintptr_t)target_start)); \
198 \
199 /* Look for any bytes still 0xFF in check region. */ \
200 for (sum = 0, i = 0; i < target_size; i++) \
201 sum += (check_buf[i] == 0xFF); \
202 \
203 if (sum != 0 && xfail) \
204 kunit_skip(test, \
205 "XFAIL uninit bytes: %d\n", \
206 sum); \
207 KUNIT_ASSERT_EQ_MSG(test, sum, 0, \
208 "uninit bytes: %d\n", sum); \
209 }
210 #define DEFINE_TEST(name, var_type, which, init_level, xfail) \
211 /* no-op to force compiler into ignoring "uninitialized" vars */\
212 static noinline DO_NOTHING_TYPE_ ## which(var_type) \
213 do_nothing_ ## name(var_type *ptr) \
214 { \
215 /* Will always be true, but compiler doesn't know. */ \
216 if ((unsigned long)ptr > 0x2) \
217 return DO_NOTHING_RETURN_ ## which(ptr); \
218 else \
219 return DO_NOTHING_RETURN_ ## which(ptr + 1); \
220 } \
221 static noinline int leaf_ ## name(unsigned long sp, bool fill, \
222 var_type *arg) \
223 { \
224 char buf[VAR_BUFFER]; \
225 var_type var \
226 INIT_ ## which ## _ ## init_level(var_type); \
227 \
228 target_start = &var; \
229 target_size = sizeof(var); \
230 /* \
231 * Keep this buffer around to make sure we've got a \
232 * stack frame of SOME kind... \
233 */ \
234 memset(buf, (char)(sp & 0xff), sizeof(buf)); \
235 /* Fill variable with 0xFF. */ \
236 if (fill) { \
237 fill_start = &var; \
238 fill_size = sizeof(var); \
239 memset(fill_start, \
240 (char)((sp & 0xff) | forced_mask), \
241 fill_size); \
242 } \
243 \
244 /* Silence "never initialized" warnings. */ \
245 DO_NOTHING_CALL_ ## which(var, name); \
246 \
247 /* Exfiltrate "var". */ \
248 memcpy(check_buf, target_start, target_size); \
249 \
250 return (int)buf[0] | (int)buf[sizeof(buf) - 1]; \
251 } \
252 DEFINE_TEST_DRIVER(name, var_type, which, xfail)
253
254 /* Structure with no padding. */
255 struct test_packed {
256 unsigned long one;
257 unsigned long two;
258 unsigned long three;
259 unsigned long four;
260 };
261
262 /* Simple structure with padding likely to be covered by compiler. */
263 struct test_small_hole {
264 size_t one;
265 char two;
266 /* 3 byte padding hole here. */
267 int three;
268 unsigned long four;
269 };
270
271 /* Trigger unhandled padding in a structure. */
272 struct test_big_hole {
273 u8 one;
274 u8 two;
275 u8 three;
276 /* 61 byte padding hole here. */
277 u8 four __aligned(64);
278 } __aligned(64);
279
280 struct test_trailing_hole {
281 char *one;
282 char *two;
283 char *three;
284 char four;
285 /* "sizeof(unsigned long) - 1" byte padding hole here. */
286 };
287
288 /* Test if STRUCTLEAK is clearing structs with __user fields. */
289 struct test_user {
290 u8 one;
291 unsigned long two;
292 char __user *three;
293 unsigned long four;
294 };
295
296 #define ALWAYS_PASS WANT_SUCCESS
297 #define ALWAYS_FAIL XFAIL
298
299 #ifdef CONFIG_INIT_STACK_NONE
300 # define USER_PASS XFAIL
301 # define BYREF_PASS XFAIL
302 # define STRONG_PASS XFAIL
303 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_USER)
304 # define USER_PASS WANT_SUCCESS
305 # define BYREF_PASS XFAIL
306 # define STRONG_PASS XFAIL
307 #elif defined(CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF)
308 # define USER_PASS WANT_SUCCESS
309 # define BYREF_PASS WANT_SUCCESS
310 # define STRONG_PASS XFAIL
311 #else
312 # define USER_PASS WANT_SUCCESS
313 # define BYREF_PASS WANT_SUCCESS
314 # define STRONG_PASS WANT_SUCCESS
315 #endif
316
317 #define DEFINE_SCALAR_TEST(name, init, xfail) \
318 DEFINE_TEST(name ## _ ## init, name, SCALAR, \
319 init, xfail)
320
321 #define DEFINE_SCALAR_TESTS(init, xfail) \
322 DEFINE_SCALAR_TEST(u8, init, xfail); \
323 DEFINE_SCALAR_TEST(u16, init, xfail); \
324 DEFINE_SCALAR_TEST(u32, init, xfail); \
325 DEFINE_SCALAR_TEST(u64, init, xfail); \
326 DEFINE_TEST(char_array_ ## init, unsigned char, \
327 STRING, init, xfail)
328
329 #define DEFINE_STRUCT_TEST(name, init, xfail) \
330 DEFINE_TEST(name ## _ ## init, \
331 struct test_ ## name, STRUCT, init, \
332 xfail)
333
334 #define DEFINE_STRUCT_TESTS(init, xfail) \
335 DEFINE_STRUCT_TEST(small_hole, init, xfail); \
336 DEFINE_STRUCT_TEST(big_hole, init, xfail); \
337 DEFINE_STRUCT_TEST(trailing_hole, init, xfail); \
338 DEFINE_STRUCT_TEST(packed, init, xfail)
339
340 #define DEFINE_STRUCT_INITIALIZER_TESTS(base, xfail) \
341 DEFINE_STRUCT_TESTS(base ## _ ## partial, \
342 xfail); \
343 DEFINE_STRUCT_TESTS(base ## _ ## all, xfail)
344
345 /* These should be fully initialized all the time! */
346 DEFINE_SCALAR_TESTS(zero, ALWAYS_PASS);
347 DEFINE_STRUCT_TESTS(zero, ALWAYS_PASS);
348 /* Struct initializers: padding may be left uninitialized. */
349 DEFINE_STRUCT_INITIALIZER_TESTS(static, STRONG_PASS);
350 DEFINE_STRUCT_INITIALIZER_TESTS(dynamic, STRONG_PASS);
351 DEFINE_STRUCT_INITIALIZER_TESTS(runtime, STRONG_PASS);
352 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_static, STRONG_PASS);
353 DEFINE_STRUCT_INITIALIZER_TESTS(assigned_dynamic, STRONG_PASS);
354 DEFINE_STRUCT_TESTS(assigned_copy, ALWAYS_FAIL);
355 /* No initialization without compiler instrumentation. */
356 DEFINE_SCALAR_TESTS(none, STRONG_PASS);
357 DEFINE_STRUCT_TESTS(none, BYREF_PASS);
358 /* Initialization of members with __user attribute. */
359 DEFINE_TEST(user, struct test_user, STRUCT, none, USER_PASS);
360
361 /*
362 * Check two uses through a variable declaration outside either path,
363 * which was noticed as a special case in porting earlier stack init
364 * compiler logic.
365 */
366 static int noinline __leaf_switch_none(int path, bool fill)
367 {
368 switch (path) {
369 /*
370 * This is intentionally unreachable. To silence the
371 * warning, build with -Wno-switch-unreachable
372 */
373 uint64_t var[10];
374
375 case 1:
376 target_start = &var;
377 target_size = sizeof(var);
378 if (fill) {
379 fill_start = &var;
380 fill_size = sizeof(var);
381
382 memset(fill_start, forced_mask | 0x55, fill_size);
383 }
384 memcpy(check_buf, target_start, target_size);
385 break;
386 case 2:
387 target_start = &var;
388 target_size = sizeof(var);
389 if (fill) {
390 fill_start = &var;
391 fill_size = sizeof(var);
392
393 memset(fill_start, forced_mask | 0xaa, fill_size);
394 }
395 memcpy(check_buf, target_start, target_size);
396 break;
397 default:
398 var[1] = 5;
399 return var[1] & forced_mask;
400 }
401 return 0;
402 }
403
404 static noinline int leaf_switch_1_none(unsigned long sp, bool fill,
405 uint64_t *arg)
406 {
407 return __leaf_switch_none(1, fill);
408 }
409
410 static noinline int leaf_switch_2_none(unsigned long sp, bool fill,
411 uint64_t *arg)
412 {
413 return __leaf_switch_none(2, fill);
414 }
415
416 /*
417 * These are expected to fail for most configurations because neither
418 * GCC nor Clang have a way to perform initialization of variables in
419 * non-code areas (i.e. in a switch statement before the first "case").
420 * https://llvm.org/pr44916
421 */
422 DEFINE_TEST_DRIVER(switch_1_none, uint64_t, SCALAR, ALWAYS_FAIL);
423 DEFINE_TEST_DRIVER(switch_2_none, uint64_t, SCALAR, ALWAYS_FAIL);
424
425 #define KUNIT_test_scalars(init) \
426 KUNIT_CASE(test_u8_ ## init), \
427 KUNIT_CASE(test_u16_ ## init), \
428 KUNIT_CASE(test_u32_ ## init), \
429 KUNIT_CASE(test_u64_ ## init), \
430 KUNIT_CASE(test_char_array_ ## init)
431
432 #define KUNIT_test_structs(init) \
433 KUNIT_CASE(test_small_hole_ ## init), \
434 KUNIT_CASE(test_big_hole_ ## init), \
435 KUNIT_CASE(test_trailing_hole_ ## init),\
436 KUNIT_CASE(test_packed_ ## init) \
437
438 static struct kunit_case stackinit_test_cases[] = {
439 /* These are explicitly initialized and should always pass. */
440 KUNIT_test_scalars(zero),
441 KUNIT_test_structs(zero),
442 /* Padding here appears to be accidentally always initialized? */
443 KUNIT_test_structs(dynamic_partial),
444 KUNIT_test_structs(assigned_dynamic_partial),
445 /* Padding initialization depends on compiler behaviors. */
446 KUNIT_test_structs(static_partial),
447 KUNIT_test_structs(static_all),
448 KUNIT_test_structs(dynamic_all),
449 KUNIT_test_structs(runtime_partial),
450 KUNIT_test_structs(runtime_all),
451 KUNIT_test_structs(assigned_static_partial),
452 KUNIT_test_structs(assigned_static_all),
453 KUNIT_test_structs(assigned_dynamic_all),
454 /* Everything fails this since it effectively performs a memcpy(). */
455 KUNIT_test_structs(assigned_copy),
456 /* STRUCTLEAK_BYREF_ALL should cover everything from here down. */
457 KUNIT_test_scalars(none),
458 KUNIT_CASE(test_switch_1_none),
459 KUNIT_CASE(test_switch_2_none),
460 /* STRUCTLEAK_BYREF should cover from here down. */
461 KUNIT_test_structs(none),
462 /* STRUCTLEAK will only cover this. */
463 KUNIT_CASE(test_user),
464 {}
465 };
466
467 static struct kunit_suite stackinit_test_suite = {
468 .name = "stackinit",
469 .test_cases = stackinit_test_cases,
470 };
471
472 kunit_test_suites(&stackinit_test_suite);
473
474 MODULE_DESCRIPTION("Test cases for compiler-based stack variable zeroing");
475 MODULE_LICENSE("GPL");
476
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